Heating, Ventilation and Air Conditioning (HVAC) systems utilize air ducts to distribute and transport air from one location to another. HVAC systems are used in residential, commercial and industrial applications. The vast majority of HVAC systems are used inside of buildings; some however are used for outside applications.
In a typical installation, ducts extend from a plenum to registers which are located in one or more rooms. The ducts can be of various lengths and diameters, and typically include turns or radiuses.
One type of air duct is made from galvanized sheet metal. The air ducts are in essence pipes. When two segments of air ducts are coupled together, a joint is formed.
It is desirable to seal the joint in order to prevent air leakage. Leaking joints reduce the overall efficiency of the HVAC system.
In the prior art, there are several ways to seal a joint coupling air ducts. By far, the least preferred is the use of duct tape. The adhesive on the tape degrades over time and with high temperatures, resulting in a loss of seal.
Duct mastic is a compound that is applied to a joint. When the mastic dries, it provides a satisfactory seal. Unfortunately, the application of duct mastic around the entire circumference of the joint is difficult to accomplish, especially when the duct is located adjacent to a ceiling, where access is difficult. Thus, the cost for sealing joints with mastic can be high due to the amount of labor involved. Furthermore, some duct mastic gives off fumes which contribute to poor air quality and even to sick building syndrome.
Still another prior seal is provided by Lindab, and is described in U.S. Pat. Nos. 4,050,703 and 5,531,460. A circumferential rubber seal is coupled to each end of air duct pipes. The two ends are joined together by a collar, which contacts the seal in each pipe. This type of seal works well. However, it is expensive to make. In addition, the seal is relatively fragile. Once the collar is placed over the seal, removing the collar may cause the seal to rip.